The skin barrier is made up of three closely packed cell layers: the epidermis, dermis, and hypodermis (upper to bottom layer). The epidermis consists of keratin, which provides mechanical strength to the skin surface, preventing enzymatic degradation. The acidic environment of the surface also prevents bacterial degradation and inhibits microbial growth. Skin shedding also sheds microbes on the skin surface. Damage to the skin barrier allows for pathogens to enter into deeper tissue.

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